基于震源机制解的鄂霍次克微板块东部俯冲带地区构造应力场反演

Inversion of Tectonic Stress Field in the Eastern Subduction Zone of Okhotsk Micro-plate Based on Focal Mechanism Solution

摘要:

基于国际地震中心（ISC）提供的1970年1月~2016年12月期间的地震震源机制解，对鄂霍次克微板块东部俯冲带地区进行了应力张量反演，得到了日本海沟、千岛海沟和勘察加海沟3个俯冲带区域的构造应力场特征。研究结果显示：①海沟地区浅部区域（h<100km）的水平主压应力轴与西北太平洋板块的俯冲方位一致，与海沟走向近似垂直，其洋壳一侧以拉张型应力状态为主，而陆壳一侧则以挤压型应力为主，且在弧后区域均存在拉张的应力状态；80~200km深度范围区域表现出双地震带“I”型构造应力场特征。②日本海沟带由于俯冲角相对较小（相比于千岛海沟和勘察加海沟），水平方向沿NWW向延伸更远，大洋板块与上覆板块之间耦合更加强烈，逆冲型地震发生数量最多。③对于深部区域（h>300km），千岛地区应力场表现出非均匀性特征，可能是由地幔阻力导致的；而勘察加地区应力场表现出拉张型，可能是因为俯冲板片的拉伸拖曳作用更强。

Abstract:

Based on the seismic focal mechanism solution from years of 1970 to 2016 provided by the International Seismological Center (ISC),we performed stress tensor inversion in the subduction zone of the eastern Okhotsk micro-plate,and obtained the characteristics of tectonic stress field in the subduction zone of the Japan trench,the Kuril trench and the Kamchatka trench. The results show that:①The principal horizontal compressive stress axis in the shallow region (h<100km) of these trenches are consistent with the subduction orientation of the northwest Pacific plate and almost perpendicular to the direction of these trenches. In the trench area,the stress state on oceanic crust side is mainly tensile,while that on the continental crust is mainly compressive. Moreover,the tensile stress state exits in all post-arc regions. The region with a depth of 80~200km shows the "I" type tectonic stress field characteristics of the double seismic zone. ②The subduction zone in the Japan trench has a lower subduction dip angle (compared with the angles of Kuril trench and Kamchatka trench),and the subduction zone also extends farther in the horizontal direction toward the NWW,which leads a strong coupling between the oceanic plate and the overlying plate,and the large number of TF earthquakes. ③In deep the subduction zone (h>300km),the stress field of Kuril area shows non-uniformity,which may be caused by mantle resistance. The stress field of Kamchatka region (h>300km) is tensional,which may be due to the relatively stronger tensile drag of subduction plates.